This project proposes to examine the role of excitatory amino acids in the retina of fish, amphibians, and mammals through the use of itracellular recording techniques. In particular, the photoreceptor and bipolar cell transmitters will be studied. Emphasis will be placed on identifying and characterizing the action of excitatory amino acids in lower vertebrates and applying these results to mammals. Excitatory amino acids will be analyzed based on chain length, sidegroup constituents, and conformation. Comparisons of putative and endogenous transmitters will be performed using antagonists, conductance measurements, reversal potential, and ionic conductances. ON-OFF channels and rod-cone pathways will be pharmacologically analyzed to determine if their separation of signals is due to different transmitters and/or post-synaptic receptors. Single cell staining will be used to develop morphological-pharmacological correlations in subgroups of retinal neurons. An analysis of retinal function will be developed by the use of selective antagonists to eliminate specific cell inputs and thus simplify the retinal network. Selective pharmacological manipulation of retinal neurons can be used to further understand the components of the ERG. This can enhance the utility of the ERG in clinical diagnosis and Ophthalmological Research.